It is well known that in many industrial applications space is at a premium, particularly storage space in warehouses, plant tool rooms and the like, and accordingly, there have been developed numerous systems for storage of various goods. In many cases, these have become industry standard so that, for example, cabinets comprising drawers of one manufacturer can be stacked or assembled with those of another manufacturer. Typically, these will be stacked higher than one can conveniently reach, so some means must be provided to provide access to the upper levels of storage. This may comprise such things as a "rolling stair," a flight of stairs mounted on casters. Typically, the casters are spring-loaded so that when one steps on the stairs, the casters retract into the supporting structure so its feet contact the floor, preventing rolling. However, this system is not always convenient. In particular, it would be desirable if permanent stairways and platforms could be provided to reach the upper level of storage structures so as to avoid use of the rolling stairs and the floor space they inevitably must take up. Furthermore, such permanent structure would simplify operations by permitting two persons at once to access the upper level of storage, whereas usually only one person at a time can employ a rolling stair.
Obviously, it would be desirable if such a mezzanine structure, i.e., a platform at height convenient to allow one to access upper levels of shelves in a relatively tall storage system, could be provided in as efficient and inexpensive fashion as possible. In particular, it would be desirable if such a system could be provided which could be added to preexisting storage structure without drilling or other machining operations, that is, by interacting with structure already found in industry-standard storage units.